Verburg & Son Dairy, 1142 N Hart Rd, Modesto, CA 95358, US

Challenge Dairy Products, established in 1911, is a cooperative association responsible for the marketing and distribution of dairy products from more than 700 family-owned dairies. The company specializes in the marketing of Challenge brand butter products. Its butter is available in several varieties that include spreadable, European style, unsalted, whipped and light. Challenge Dairy Products is a wholly owned subsidiary of California Dairies. California Dairies engages in the manufacture and supply of butter for major food producers in sizes ranging from large bulk boxes to small cups for restaurant dining. In addition, the company markets dry milk powders through DairyAmerica that include nonfat dry milk, dry buttermilk and dry whole milk. Challenge Dairy Products is located in Dublin, Calif.